Conventionally, immunoassay in which a trace substance is detected by utilizing antigen-antibody reaction has been known. Moreover, recently, antibody medicines utilizing functions of antibodies have been actively developed. Such antibody medicines have excellent effects and less adverse effects, and act on various drug targets. Moreover, the antibody medicines can be industrially produced. Accordingly, the antibody medicines are drawing attentions, as a technology that allows quickly providing a treatment against target molecules found in genome researches. The antibody medicines have various functions of, for example, a blocking antibody that is combined to a receptor or a ligand and inhibiting signaling, a signaling antibody that is combined to a receptor and shows a receptor crosslinking effect, and a targeting antibody having ADCC activity or CDC activity and therefore having cytotoxicity.
Development of such antibody medicines generally starts with gene search followed by identification of an antigen that becomes a target of an antibody medicine, preparation of an antibody that binds specifically to the antigen, check of a pharmacological effect of the antibody, and ultimate mass production of the antibody medicine. In this development flow, a process of screening an antibody that binds specifically to an antigen is considered important.
As a technique for screening antibodies, a method employing phage display is known. This method is a technique in which: first, an antibody library presenting various antigen-specific antibodies on phages is prepared; and then, screening of antibodies that binds specifically to a specific antigen is carried out (See Patent Literature 1, for example).